1. Field of the invention
The present invention is generally concerned with clutch release bearings of the type fitted to automobile vehicles, for example.
2. Description of the prior art
Known clutch release bearings generally comprise a maneuvering member which is adapted to be operated on by a control member, in practise a clutch release yoke, and a drive member in direct or indirect axial bearing engagement with the maneuvering member and which is adapted, when operated on by the latter, to operate on the clutch release device of a clutch.
The present invention is more particularly directed to the case where the drive member is urged axially against the maneuvering member by a bistable axially acting spring washer, in other words an axially acting spring washer adapted to turn inside out selectively so as to assume one or other of two separate stable configurations one of which is a concave configuration and the other of which is a convex configuration and one of which is an inoperative configuration and the other of which is an operative configuration, said concave and convex configurations being defined relative to the same axial observation direction.
A clutch release bearing of this type is described, for example in U.S. Pat. No. 4,608,741.
The spring washer used in it is adapted to have one of its peripheral edges bear axially on the drive member in the operative configuration and has on its other peripheral edge at least one lug through which it is adapted to bear against the maneuvering member.
In some at least of the embodiments envisaged, this lug is in a dihedral relationship to the remainder of the spring washer of which it forms part.
Being substantially rectilinear, for example, it is intended to be braced through the edge of one end against a shoulder on the maneuvering member with the concave side of the dihedron which it forms with the spring washer facing axially away from the side of the spring washer through which the latter bears axially on the drive member in the operative configuration.
In an alternative arrangement it is provided at its end with a right-angle lip and is intended to be hooked over the maneuvering member with the concave side of the dihedron that it forms with the spring washer facing axially towards the side of the spring washer through which the latter bears axially on the drive member in the operative configuration.
Such use of a bistable axially acting spring washer has the advantage of facilitating assembly: with the axially acting spring washer in the inoperative configuration within the drive member, of which it forms part from the outset of the assembly process, the drive member and the maneuvering member are engaged together axially and, on completion of such axial engagement, the spring washer goes of its own accord to the operative configuration with its lug or lugs braced against or hooked onto the maneuvering member.
The corresponding arrangement had proven and may yet prove satisfactory.
However, it has the disadvantage of leading to non-negligible mechanical stressing of the root area through which the lug or lugs on the Belleville spring washer merge with the remainder.
During assembly, the dihedral angle between the lugs and the spring washer changes value several times.
Taking the example of rectilinear lugs designed to be operative in braking, this angle is initially, in the inoperative configuration, considerably larger than 90.degree., being in practise near 180.degree.. It is first reduced to a value of less than 90.degree. during the first phase of relative engagement between the drive member and the maneuvering member. It then returns to a value greater than 90.degree. when, at the end of such engagement, the spring washer turns inside out to assume the operative configuration.
The corresponding mechanical stresses may lead to fracture.
A general object of the present invention is an arrangement which makes it possible to avoid this disadvantage while making it possible to retain the advantage of assembly by simple relative axial interengagement of the drive member and the maneuvering member.